Floating piston hydraulic pump



Nov. 22, 1966 s. c. DAUBIN FLOATING PISTON HYDRAULIC PUMP 2 Sheets-Sheet 1 Filed Jan. 31, 1964 IN V E NTOR. Zvza C fiauzzy ATTORNEY s. c. DAUBIN FLOATING PISTON HYDRAULIC PUMP Nov. 22, 1966 2 Sheets-Sheet 2 Filed Jan. 31, 1964 m I fl INVENTOR. $605 6 C flea 5x2? BY .4 TTORNF Y United States Patent 3,286,638 Patented Nov. 22, 1966 3,286,638 FLOATING PISTON HYDRAULIC PUMP Scott C. Daubin, Santa Barbara, Calif., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 31, 1964, Ser. No. 341,609 Claims. (Cl. 103-38) This invention relates to pumps and more particularly to a variable capacity pump wherein both the pump capacity and pump pressure discharge may be easily and simply controlled and wherein the maximum pump discharge pressure may be regulated during pumping operation.

In certain pump installations it is desirable to be able to vary the maximum pump discharge pressure obtainable and to automatically terminate pumping action upon attainment of a desired pump discharge pressure in a system being supplied by the pump. It is further desirable to be able to vary maximum pump discharge pressure during pump operations and while the pump is being driven.

An object of this invention is to provide a pump wherein the maximum pump discharge pressure may be manually varied during pump operation and Without interrupting drive of the pump.

Another object of this invention is to provide a pump wherein the maximum fiow rate and direction may be manually varied during pump operation and without interrupting drive of the pump.

A further object of this invention is to provide a pump adapted to be driven by a unidirectional power source and having manually controlled means for reversing the pumping action when so desired.

A particular object of this invention is to provide a pump incorporating an eccentric cam and a free floating piston driven by the cam wherein the cam eccentricity may be manually varied to vary the pump capacity.

A more particular object of this invention is to provide a pump having a free floating piston biased in one direction by a rotating cam and biased toward contact with the cam by means of controlled pressure acting upon one end of the piston.

A further object of this invention is to provide manually controlled means for varying the controlled pressure acting upon the piston of a cam driven pump for varying the maximum pump discharge pressure deliverable by the pump.

A further object of this invention is to provide a basic pumping unit which can be attached to other pumping units of the same design on the same shaft and driven by the same power source, thus multiplying the pumping capacity.

A further object of this invention is to provide an inherently safe pump which is self-relieving without the use of a relief valve, i.e., if the discharge pressure rises above a certain value, as might occur if a discharge valve was inadvertently shut while the pump was running, the pumping action would automatically cease.

A further object of this invention is to provide an inherently quiet pump which by the floating piston concept tends to smooth out pressure pulsations which are inherent in rigidly connected piston type pumps.

' These and other objects of this invention will become more apparent as reference is had to the accompanying specification and drawings wherein:

' FIGURE 1 shows the novel pump connected with the associated air source and control systems.

FIGURE 2 is a sectional view of the novel pump taken substantially along the line 22 of FIGURE 1, with sections broken away, showing gearing for varying the eeative to the blocks.

centricity of the cam and the internal location of the components of the pump.

FIGURE 3 is a view taken substantially along the line 33 of FIGURE 2, with sections broken away, showing a cross section of the shaft having intake and exhaust chambers located therein.

FIGURE 4 is a view taken substantially along the line 4-4 of FIGURE 2 illustrating the radial position of the pistons and cylinders about the central drive shaft with the eccentric in one of its extreme positions.

FIGURE 5 is the same view as FIGURE 4 with the eccentric in its neutral position.

In this description similar parts will have the same identification numerals. The pump to be described may be utilized for many liquids, but for ease of explanation the liquid being pumped shall be referred to as oil. Further any compressible gas or fluid would be acceptable for biasing the pistons for return movement but in the description air shall be used throughout.

Referring now to the drawings, as best seen in FIG URES l and 2, the pump assembly has a housing consisting of several sections joined together and including a cylinder block 10 having a pluarity of cylinders or cylindrical recesses 12 formed therein, the recesses 12 being arranged in one radial plane and spaced equidistantly about a central cavity 11. The cylindrical recesses 12 extend radially outward from the central cavity 11 of the cylinder block 10 and are each adapted to receive a cylinder cap 14 in the outer end to form a closed cylinder. Disposed for reciprocatory movement in each of the cylinders are piston members 16. Each piston 16 freely floats in one of the cylinders 12 there being a chamber 15 between one end of piston 16 and cap 14 and a second chamber 17 between an end wall 17a of cylinder block 10 and the opposite end of piston 16. Each piston has a piston actuating rod 18 which extends through an aperture 20 of its respective end wall 17a for contacting a common piston actuating cam 22. Each chamber 15 is connected to a suitable source of compressed fluid under pressure such as an air pump or tank of compressed air by means of a port 24 and piping 36.

As best seen in FIGURE 1, the compressed air source of this embodiment consists of an air pump 26 which supplies air under pressure through a pipe 28 to an accumulator tank 30. The tank 30 has a relief valve 32 and also is connected to a pressure control valve 34 by a pipe 36. The control valve 34 is used to control the air pressure supplied to the cylindrical chambers 15 through ports 24 by a pipe 36, as indicated on a pressure gauge 38 which is connected to pipe 36.

Referring again to FIGURE 2, a porting block 40 is secured to the cylinder block 10 by a plurality of bolts 42. A series of spaced oil distributing ports 44 extend radially outwardly within the porting block 40 and are positioned so that each oil distributing port is connected by a liquid passageway 46 to one of the chambers 17 at the inner end of one of the pistons 16. An oil seal 48 is positioned about each passage 46 between the port block 40 and the cylinder block 10 to prevent the escape of oil from the passage.

An external coupling block 50 is secured to the porting block 40 by a plurality of bolts 52. A pair of external ports 54, 56 extend outwardly from the inner surface of the external coupling block to the outer surface thereof. A pair of external pipes 58, 60 are secured to the external coupling block 50, in alignment with external ports 54, 56, respectively, by bolts 62.

. Centrally jounaled within coupling block 50, porting block 40 and cylinder block 10 is a shaft 64. The shaft 64 is journaled in a series of bearings 66, for rotation rel- Oil seals 67 are spaced along the 3 shaft to prevent oil leakage during pumping operations. As best seen in FIGURE 3, the shaft 64 is divided into two chamber 68 and '76 by a center partition '72. Referring again to FIGURE 2, one end of shaft 64 has a shaft coupling flange 74 for connecting the shaft to a power source and the other end of the shaft has a cap '76 threadably secured thereto. The coupling flange 74 may be replaced by a suitable coupling member for joining another similar pump. The cap 76 maybe removed and the threads on the shaft may be used to join another similar pump having suitable coupling members to form a series of pumps in a stacked relation so that they may pump together simultaneously.

A series of distributing liquid passages are formed in the walls of shaft 64 for the flow of liquid between the external ports 54, 56 and the liquid distributing ports 44 through chambers 68 and 78, as best seen in FIGURE 2. Passage '78 is longitudinally aligned with port 54 and connects port 54 with chamber '78, passage 80 is longitudinally aligned with port 56 and connects chamber 68 'with port 56.

Passage 82 connects chamber '70 to the liquid distributing ports 44 and passage 84 connects chamber 68 with the liquid distributing ports 44.

The piston actuating cam 22 is adjustably supported around shaft 64 by a cam guide disc 86 which is keyed to shaft 64. The cam guide disc has a pair of slots 88, as best seen in FIGURES 4 and 5, for slidably receiving a pair of cam guide keys 90 attached to the piston actuating cam 22. A cam position control shaft 92 has one end threadably engaging the piston actuating cam 22 for adjusting the eccentricity of the cam and holding the cam in the adjusted position. The other end of the cam positioning control shaft is journaled for rotation in the shaft 64. 'Adjacent the journaled end, a beveled gear 94 is secured to the control shaft 92. A retainer arm 96 extends from cam guide disc 86 and bears against the beveled gear 94 for retaining the cam positioning shaft 92 in journaled engagement with shaft 64. A shaft idler gear 98 is movably held on shaft 64 in meshing engagement with beveled gear 94 by retainers 100.

In lieu of the retainer arm 96, a similar second unit consisting of a second control shaft 93, with opposite threads would threadably engage cam 22 and a second gear 94 would be in meshing engagement with idler gear 98. The second unit would be mounted diametrically opposite the first unit about shaft 64 and help maintain the cam 22 in proper operating position.

A gear drive housing 102 is secured to the cylinder block by a plurality of bolts 104. A gear drive housing cap 106 is secured to the gear drive housing by a plurality of bolts 188 to form a chamber 110 for accommodating a differential drive assembly, indicated generally by the numeral 112, for adjusting the eccentricity of the piston actuating cam 22 by rotating the cam positioning control shaft 92.

The differential drive assembly 112 includes a drive ring gear 114 keyed to shaft 64 by a key 116. The gear 114 drives a differential drive beveled gear 118 and a differential input gear 120 fixed to gear 118 by a stub shaft 122 which is also journaled in cap 106. A pair of differential output gears 124, 126 mesh with the differential input gear 120 and with a differental bevel gear 128 which is rigidly connected to a control Worm gear 130. The differential bevel gear 128 and control worm gear 130 are rotatably mounted on a differential carrier 134. The differential beveled gears 124, 126 drive on idler drive bevel gear 132 by means of the differential carrier 134. The end of the differential carrier 134 is journaled in the gear drive housing 102 adjacent gear 132. The idler drive bevel gear 132 is in mesh with the shaft idler gear 98. Thus, it can be seen that, as the shaft 64 rotates bevel gear 94 moves therewith causing idler gear 98 to rotate with the shaft. Drive ring gear 114 also retates with shaft 64 causing differential drive bevel gear 118 and differental input gear to rotate, whereby all the gears are rotated together as the shaft rotates.

To change the eccentricity of the piston actuating cam 22 when the pump is not rotating, a worm key, not shown, is manually engaged with control Worm gear for manually rotating gear 130 and differential bevel gear 128. Since .gear 118 is not rotating, the output gears 124, 126 are driven by gear 128. Rotation of gears 124, 126 rotate idler bevel gear 132 through the differential carrier 134 and gear 132 rotates shaft idler gear 98 to rotate bevel gear 94 and adjust the eccentricity of the piston actuating cam 22 by screwing the shaft 92 into or out of the cam thereby sliding the cam guide keys 90 in slots 88 and moving the cam relative to the shaft.

To change the eccentricity .of the piston actuating cam 22 when the pump is operating, a worm key, not shown, is manually engaged with .control worm gear 13.... Movement of the worm key will rotate control worm gear 130 and differential bevel gear 128. Such rotation will increase or decrease the rotation of the differential gears 124, 126, thereby causing the differential carrier to move the idler driving gear at a different rate than the drive gear 118. The different rate will cause shaft idler gear to rotate relative to shaft 64, thereby causing gear 94 to rotate the cam positioning shaft 92 and alter the eccentricity of the cam 22.

Each cylinder 12 has a tell-tale port 136 located between the lands of the piston for indicating any leakage of the respective piston by leaking air if the piston is leaking at the outer end, and by leaking .oil if the piston is leaking at the inner end.

In operation of this pump, there are two control variables, piston actuating cam eccentricity and air pres sure. If the air pressure is fixed .and the cam eccentricity is variable, the pump acts as a variable displacement pressure limited pump. If the cam eccentricity is fixed and the air pressure variable, the pump acts as a variable pressure displacement limited pump. If the cam eccentricity is variable and the air pressure is variable, the pump acts as a variable displacement pressure compensated pump.

In the operation of the pump, a unidirectional or reversible power unit may be connected to shaft 64 to drive the pump. As the shaft is rotated, the piston actuating cam 22 rotates with the shaft 64 in the cavity 11 of the cylinder block 10. The piston actuating cam may be concentric or eccentric with the shaft and its position relative to the axis of the shaft is controlled by the control shaft 92 as adjusted by the manual operation of the differential control assembly 112. When air pressure is supplied to the outer chambers 15 of the cylinders 12 through air ports 24 from the air source, all of the pistons are urged toward the shaft 64 until their piston rods 18 contact the outer periphery of the piston actuating cam 22. If the piston actuating cam 22 is concentric with the shaft 64, during rotation of the shaft none of the pistons are moved reciprocably in their respective cylinders and no oil is pumped. If the piston actuating cam 22 is eccentric relative to shaft 64, when the shaft 64 rotates the piston rods in contact with the cam move the pistons 16 toward the outer end of the cylinder 12 as the point of the piston actuating cam farthest from the center of shaft 64 passes each respective piston and the air pressure in chamber 15 returns the piston to the inner ends of the cylinder as the point of the cam closest the center of shaft 64 passes. During such reciprocable action on the pistons, the oil is pumped. As each piston is pushed radially outward, it sucks oil into chamber 17. The oil comes from the external pipes 58 or 60 depending upon the direction of rotation of shaft 64 or the direction the control shaft 92 had moved the piston actuating cam 22 from the concentric position.

Oil flows int-o and from the pump through the ports 54 and 56 in the external coupling block 50. If the oil distributing port 44 is aligned with distributing liquid passage 82 during outward movement or intake stroke of the piston 16, oil will flow into the pump from external pipe 58, through external port 54, passage 78, into chamber 70, through chamber 70 to liquid passage 82 and thence through oil distributing port 44, through oil passageway 46 to the chamber 17 as the piston is moved away from shaft 64 by means of the piston rod 18 bearing on piston actuating cam 22. During the pumping or output stroke, as the piston actuating cam 22 rotates with the shaft 64 and the air pressure in chamber 15 forces the piston inwardly against the piston actuating cam, the oil is pumped by such inward movement of the piston from chamber 17 back through oil passageway 46, through oil distributing port 44, through liquid passage 84 and which has been moved into position adjacent oil distributing passage 44, by the rotation of shaft 64, into and through chamber 68, through passage 80, through external port 56, and delivered under pressure from the pump through external pipe 60.

The maximum delivered oil pressure of the pump can be controlled by regulating the air pressure for moving the pistons inwardly. When a desired output pressure is reached, the back pressure of the oil in chamber 17 would balance the pressure of the air in chamber 15 and after one revolution of the piston actuating cam, the pistons would be held at their outermost position by the back oil pressure and there would be no more pumping until either the air pressure was increased or the back pressure of the oil was decreased. This floating piston feature also acts as a safety factor should an output control valve be inadvertently closed, the pressure could not be excessively built up in the system.

The air space above the pistons for urging the pistons toward the shaft is relatively large and provides an almost unchanging spring constant for a given air pressure which tends to provide a quieter acting pump because the pressure transients due to each piston displacement are reduced.

The volume of oil pumped by each revolution of the shaft may be controlled by varying the eccentricity of the piston actuating cam, thereby controlling the distance the pistons move in their respective cylinders.

While but one embodiment of the invention has been shown and described, it will be evident that numerous changes and modifications may be made. It is therefore to be understood that it is not intended to limit the invention to the embodiment shown but only by the scope of the following claims.

I claim:

1. In combination, a pump comprising a housing, a cylinder in said housing, a rotatable shaft in said housing, a piston freely movable for reciprocatory movement in said cylinder, a first chamber in said cylinder at one end of said piston, cam means driven by said shaft for moving said piston in one direction in said cylinder, a second chamber in said cylinder at the end of said piston opposite said first chamber, a suction passage, a pressure delivery passage, said cam being effective upon rotation of said shaft for moving 'said piston to draw fluid into said second chamber from said suction passage, a source of compressible fluid under pressure connected to said first chamber, said fluid pressure in said first chamber being effective for moving said piston in the opposite direction for forcing fluid from said second chamher to said pressure delivery passage upon further rotation of said shaft, means for varying the pump capacity including differential gearing for varying the cam eccentricity, thereby varying the effective stroke of said piston, and means for varying the pressure of the fluid in said first chamber for controlling the maximum pressure delivered by said pump.

2. A pump comprising a housing, a cylinder block forming a portion of said housing and having a central cavity, a plurality of cylinders radially spaced about said central cavity in said cylinder block, a piston positioned in each of said cylinders for reciprocating motion therein, whereby outward movement of said piston in said cylinder will be an intake stroke and inward movement will be a pumping stroke, each of said piston having a piston rod having one end secured to said piston and a free end extending from said associated cylinder through an aperture in said cylinder block into said central cavity, a shaft rotatably mounted centrally of said cavity, a piston actuating cam adjustably secured to said shaft for rotation therewith, said cam being adjustable between a concentric position and eccentric positions relative to said shaft, said piston actuating cam being positioned on said shaft for contacting the free ends of said piston rods for moving said pistons away from said central cavity during rotation of said shaft when said cam is eccentric to said shaft, means for supplying fluid under pressure to one end of said cylinders for biasing said pistons toward said central cavity, and means for supplying a liquid to the other end of said cylinder during the intake stroke and for receiving the liquid during the pumping stroke.

3. A pump comprising a housing, a cylinder block forming a portion of said housing and having a central cavity, a plurality of cylindrical recesses radially spaced about said central cavity in said cylinder block, a piston positioned in each of said cylindrical recesses for reciprocating motion therein, whereby outward movement of said piston in said cylindrical recess will be an intake stroke and inward movement will be a pumping stroke, each of said pistons having a piston rod having one end secured to said piston and a free end extending from said associated cylindrical recess through an aperture in said cylinder block into said central cavity, a shaft rotatably mounted centrally of said cavity, a piston actuating cam adjustably secured to said shaft for rotation therewith,

said cam being adjustable between -a concentric position and eccentric positions relative to said shaft, said piston actuating cam being positioned on said shaft for contact ing the free ends of said piston rods for moving said pistons away from said central cavity during rotation of said shaft when said cam is eccentric to said shaft, means for supplying fluid under pressure to one end of said cylindrical recesses for biasing said pistons toward said central cavity, means for supplying -a liquid to the other end of said cylindrical recess during the intake stroke and for receiving the liquid during the pumping stroke, and means for varying the fluid pressure to the one end of said cylindrical recesses for controlling the maximum pressure delivered during the pumping stroke.

4. A reversible variable displacement pump having a unidirectional power source and comprising a housing including a fixed cylinder block having a central cavity and a plurality of cylinders radially spaced in the same plane outwardly from said cavity, a plurality of apertures in said cylinder block, each of said apertures extending radially from said cavity and connecting one of said cylinders thereto, a piston positioned in each cylinder for reciprocatory movement therein and having a portion thereof extending into said cavity through one of said apertures, outward movement of said piston in said cylinder being a suction stroke and inward movement a pumping stroke, a drive shaft operably connected to said power source and extending longitudinally through the center of said cavity substantially normal to the plane of said cylinders, said shaft being rotatably secured to said cylinder block for rotation about its longitudinal axis, an adjustable cam attached to said shaft for rotation therewith, said cam being in the same plane as said cylinders for contacting said portion of said pistons within said cavity for moving said pistons outwardly in said cylinders, said cam having a concentric position and a plurality of eccentric positions relative to the axis of said shaft, an adjustment means connected to said shaft and said cam and being disposed therebetween for adjusting the eccentricity of said cam for controlling the stroke of said pistons during rotation of said shaft, and fluid pressure biasing means connected to the outer end of each of said cylinders for urging said piston into contact with said cam and for moving said pistons inwardly.

5. In combination, a power source, a compressed air source and a pump comprising a pair of external ports for delivering and receiving a liquid, a drive shaft operably connected to said power source for rotation about its longitudinal axis and having a pair of chambers therein extending parallel to the longitudinal axis thereof for delivering and receiving liquid, each of said chambers having a pair of ports for connecting each of said chambers with the exterior of said shaft, one port of each chamber being aligned with one of said external ports, a cylinder block having a central cavity, a plurality of cylindrical recesses extending outwardly and being radially spaced in the same plane about said cavity, a plurality of apertures extending radially from said cavity, each of said apertures connecting one of said recesses to said cavity, a plurality of air ports, each air port connecting an :outer end of one of said recesses with said air source, bearing means for rotatably supporting said drive shaft in the center of said cavity, a plurality of liquid passages, each passage connecting an inner end of one of said recesses for alignment with the other of said ports of each of said chambers, a piston slidably mounted in each cylindrical recess for reciprocatory movement therein, said pistons having an intake stroke and an output stroke, said intake stroke being movement of said piston in one direction and said output stroke being movement of said piston in the other direction, one of said chambers being aligned with said liquid passage during said intake stroke and the other of said chambers being aligned with said liquid passage during said output stroke, a piston rod secured to each piston and extending through said aperture of said recess into said central cavity, an adjustable cam attached to said shaft for rotation therewith, said .cam being in the plane of said cylindrical recesses for contacting said piston rods vfor moving said pistons outwardly in their respective cylindrical recesses during rotation of said shaft whereby liquid is sucked into the vacated space of each cylindrical recess from said liquid passage by the outward movement of the respective piston, adjustment means connected to said cam and said shaft and being disposed therebetween for adjusting the periphery of said cam relative to the axis of rotation of said shaft whereby the eccentricity of said cam will determine the extent of outward piston movement during rotation of said shaft thereby controlling the pump capacity, air pressure from said air source biasing said piston toward said cam for moving said piston toward said cam as the periphery of said cam retracts from said piston at its outermost movement whereby the liquid sucked into the recess by the outward movement of said piston is pumped back into the liquid passage by the return of the piston, and control means for controlling the pressure .of air supplied to the outer end of said recesses for controlling the maximum pressure delivered by said pump.

References Cited by the Examiner UNITED STATES PATENTS 1,239,059 9/1917 Sundh 103-'38 1,321,086 1 l .1919 Centervall 1'03-38 2,040,667 5/1936 Moulet .1 03--38 2,356,993 8/ 1944 Glasner l=03174 2,417,474 3 1'947 Feroy 103-8 8 2,900,839 8/1959 Mackintosh 103-38 2,93 6,588 5/ 1960 Van Gerpin 103-3 8 FOREIGN PATENTS 569,759 6/ 1945 Great Britain. 79,625 11/ 1955 Netherlands.

LAURENCE V. EFNER, Primary Examiner. 

1. IN COMBINATION, A PUMP COMPRISING A HOUSING, A CYLINDER IN SAID HOUSING, A ROTATABLE SHAFT IN SAID HOUSING, A PISTON FREELY MOVABLE FOR RECIPROCATORY MOVEMENT IN SAID CYLINDER, A FIRST CHAMBER IN SAID CYLINDER AT ONE END OF SAID PISTON, CAM MEANS DRIVEN BY SAID SHAFT FOR MOVING SAID PISTON IN ONE DIRECTION IN SAID CYLINDER, A SECOND CHAMBER IN SAID CYLINDER AT THE END OF SAID PISTON OPPOSITE SAID FIRST CHAMBER, A SUCTION PASSAGE, A PRESSURE DELIVERY PASSAGE, SAID CAM BEING EFFECTIVE UPON ROTATION OF SAID SHAFT FOR MOVING SAID PISTON TO DRAW FLUID INTO SAID SECOND CHAMBER FROM SAID SUCTION PASSAGE, A SOURCE OF COMPRESSIBLE FLUID UNDER PRESSURE CONNECTED TO SAID FIRST CHAMBER, SAID FLUID PRESSURE IN SAID FIRST CHAMBER BEING EFFECTIVE FOR MOVING SAID PISTON IN THE OPPOSITE DIRECTION FOR FORCING FLUID FROM SAID SECOND CHAMBER TO SAID PRESSURE DELIVERY PASSAGE UPON FURTHER ROTATION OF SAID SHAFT, MEANS FOR VARYING THE PUMP CAPACITY INCLUDING DIFFERENTIAL GEARING FOR VARYING THE CAM ECCENTRICITY, THEREBY VARYING THE EFFECTIVE STROKE OF SAID PISTON, AND MEANS FOR VARYING THE PRESSURE OF THE FLUID IN SAID FIRST CHAMBER FOR CONTROLLING THE MAXIMUM PRESSURE DELIVERED BY SAID PUMP. 